In the figures, the first digit of a reference numeral will indicate the first figure in which that element is discussed.
This invention relates in general to female electrical contacts and relates more particularly to slotless female contacts that are suitable for use in the inner conductor of a connector that, at microwave frequencies, does not introduce variable performance that can limit resolution of an instrument utilizing such a connector.
In FIG. 1 is illustrated connection between a pair of prior art connectors 10 and 10', each having a female contact at the end of its inner conductor. Connector 10 comprises an outer conductor 11, an inner conductor 12 and a slotted collet 13 that is partially contained within a cavity 14 in the inner conductor. Slots 15 in collet 13 enable it to make contact with inner conductor 12 at a point 16 substantially at the front face of inner conductor 12 and to enable it to be pressed into cavity 14 in response to pressure from a collet 13' in second connector 10' to which first connector 10 is connected. Analogous elements of connector 10' are indicated by corresponding primed reference numerals.
Unfortunately, mated front faces 17 and 17' of the collets may not be coplanar with the mated ends 19 and 19' of the outer conductors 11 and 11'. If collet 13 is stiffer than collet 13', then, as illustrated in this figure, collet 13 will extend farther outward from cavity 14 than does collet 13' from cavity 14'. Thus, near the end of each of these connectors, the impedance experienced by a microwave signal will depend on the interaction between the two inner conductors. If connector 10 were instead connected to a different connector, then collet 13 would wind up protruding more or less than it does when connected to connector 10' and thereby exhibit a different impedance for that connection.
Microwave signals have a small enough wavelength that the spatial variation in the diameter of the inner conductor between planes 19 and 110 will produce a spatially varying impedance in that region. A reference termination can be coupled to connector 10 to enable an instrument to be calibrated to compensate for this spatial variation between planes 19 and 110. However, this calibration will be meaningful only if this spatial variation is unchanged when the reference termination is replaced by another connector used during actual measurements. Because the connector of FIG. 1 exhibits an impedance that is dependent on what it is coupled to, such calibration cannot completely compensate for the spatial variation of the inner conductor. Existing measuring instruments are sufficiently sensitive that such variable impedance can limit the sensitivity of the measuring device.
In FIG. 2 is shown a female connector 20 that is suitable for use at microwave frequencies (See U.S. Pat. No. 4,797,126 entitled "Adjustable Length Slotless Female Contact For Connectors" issued to Julius Botka on Jan. 10, 1989). In this connector, a collet 23 is designed such that this collet repeatedly makes contact with a wall 211 of inner conductor 22 at a point 26 that is substantially independent of the parameters of a male pin that is inserted through an end 27 of this connector. This female connector therefore has very favorable operating characteristics, but it does have several drawbacks. The inner conductor contains a collet design that is substantially larger in diameter than the range of male pin diameters that it can accommodate. Therefore, it is not suitable to applications where the ratio of the diameter of the female contact to the diameter of the male contact must be low.
Also, there are some situations in calibration where a coaxial airline is used in which no dielectric support is included to hold the inner conductor concentric with the outer conductor. For such reference terminations, the inner conductor lies on the bottom of the inner wall of the outer conductor. It is difficult to properly connect both ends of the airline. When one end of the airline is connected to another device, that end is supported by the other device, but the other end continues to droop onto the inner surface of the airline's outer conductor. In coupling a second device to the unsupported end of the airline, as the airline and this second device are brought into close proximity for coupling, it is difficult to peer inside of the airline to properly guide mating of the center conductors. This makes it difficult to accomplish such additional coupling without damaging the center conductor of the airline. A design would therefore be useful that overcomes this difficulty.